Servo Bias Input And Wiring; Dsp-Controlled Input Limiter; Dbu Block Diagram - Lectrosonics DBu Instruction Manual

Servo Bias Input and Wiring

The DBu input preamp is a unique design that delivers
audible improvements over conventional transmitter
inputs, is easier to use and much harder to overload.
It is not necessary to introduce pads on some mics
to prevent overload of the input stage, divide the bias
voltage down for some low voltage mics, or reduce the
limiter range at minimum gain settings.
Two different microphone wiring schemes are available
to simplify and standardize the configuration. Simpli-
fied 2-wire and 3-wire configurations provide several
arrangements designed for use only with servo bias
inputs to take full advantage of the preamp circuitry.
Other wiring schemes are compatible with Servo Bias
and conventional inputs.
A line level input wiring provides an extended frequency
response with an LF roll-off at 35 Hz for use with instru-
ments and line level signal sources.

DBu Block Diagram

+5V
Servo Bias
Supply
Input
Jack
Input
Preamp
Gain
Adj
Shunt
Limiter Control
Limiter
PLL Ref
Oscillator
VCTXO
36.864 mHz
Consumer Alert for US Users - FCC Order DA 10-92
Most users do not need a license to operate this wireless microphone system. Nevertheless, operating this microphone system
without a license is subject to certain restrictions: the system may not cause harmful interference; it must operate at a low power
level (not in excess of 50 milliwatts); and it has no protection from interference received from any other device. Purchasers
should also be aware that the FCC is currently evaluating use of wireless microphone systems, and these rules are subject to
change. For more information, call the FCC at 1-888- CALL-FCC (TTY: 1-888-TELL-FCC) or visit the FCC's wireless microphone
website at www.fcc.gov/cgb/wirelessmicrophones. To operate wireless microphone systems at power greater than 50mW, you
must qualify as a Part 74 user and be licensed. If you qualify and wish to apply for a license go to: http://www.fcc.gov/Forms/
Form601/601.html
Rio Rancho, NM
DBu Transmitter
Bias Voltage
0, 2 or 4V
A-D
Converter
HI/Lo
Audio
Pass
Filter
I2S
Microprocessor
Key Received
Blue LED
Phase Locked Loop

DSP-controlled Input Limiter

The transmitter employs a digitally-controlled analog
audio limiter prior to the analog-to-digital converter.
The limiter has a range greater than 30 dB for excellent
overload protection. A dual release envelope makes the
limiter acoustically transparent while maintaining low
distortion. It can be thought of as two limiters in series,
connected as a fast attack and release limiter followed
by a slow attack and release limiter. The limiter recovers
quickly from brief transients, so that its action is hidden
from the listener, but recovers slowly from sustained
high levels to keep audio distortion low and preserve
short term dynamic changes in the audio.
D-A Convert-
er I + Q
Baseband
Signals
I2S
(2) AA
Batteries
Firmware
Update
UART
Security Key
Keypad
Voltage Controlled
Oscillator
Control
Digital Belt-Pack Transmitter
Low
pass
filters
Switching
Power
Supply
Power
LED
Tricolor
IR Port
USB
Jack
IQ Modulator
Low
Buffer
Pass
Filter
Filters
Final
Amplifier
3